ITEC 274 Final Exam Questions &
Answers
Peripheral - ANSWERSdevices are input / output / storage communication devices that connect
to the computer's primary computing devices of the processor and main memory (can be
internal or external)
Device management - ANSWERSinvolves overseeing the delicate balance of the system's finite
supply of devices with the user's almost infinite demand for them
The four basic functions of Device Management - ANSWERS1. Monitoring the status of each
device
2. Enforcing present policies to determine which process gets device and for how long
3. Allocating each device
4. Deallocating each device
bit manipulators - ANSWERSComputers are digital data processors used to turn data into
information.
Computers use at least 3 ways to represent bits - ANSWERSMagnetic, Optical, or Electricity
Magnetic - ANSWERS+ - charge
Optical - ANSWERSabsence or presence of reflective light
Electricity (voltage) - ANSWERSsolid state
,From the OS perspective there are three device types - ANSWERSDedicated, Shared, and Virtual
Dedicated device - ANSWERSAssigned to one job at a time:
- for entire time that job is active (or until released)
- EX. tape drivers, printers, and plotters
Disadvantage:
- must be allocated for duration of job execution - inefficient if device not used 100 percent of
time
Shared device - ANSWERSAssigned to several processes.
- EX. direct access storage device (DASD)
Virtual device - ANSWERSDedicated and shared device combination - dedicated device
transformed into shared device
EX. printer
- converted by spooling program
Spooling - ANSWERSspeeds up slow dedicated I/O device
OS Device Manager divides I/O task into 3 parts - ANSWERSI/O traffic controller, scheduler, and
handler
I/O traffic controller - ANSWERS- Watches status of devices, control units, channels
- Three main tasks:
1. Determine if path available
, 2. If more than one path available, determine which one to select
3. If paths all busy, determine when one is available
- Maintains database containing each unit's status and connections
I/O schedular - ANSWERS- Similar job as process scheduler
- Allocates devices, control units, and channels
- If requests greater than available paths (decides which request to satisfy first: based on
different criteria)
I/O device handler - ANSWERS- Performs actual data transfer
1. Processes device interrupts
2. Handles error conditions
3. Provides detailed scheduling algorithms
- Device dependent
Storage devices are classified by several factors - ANSWERSType of medium: magnetic, optical,
solid state
Access Method: sequential, direct
Capacity: how much can be stored (# bytes)
Access Time: how fast can save \ retrieve data
etc (fixed \ removable).
Sequential Access Storage Media - ANSWERSMagnetic tape
Answers
Peripheral - ANSWERSdevices are input / output / storage communication devices that connect
to the computer's primary computing devices of the processor and main memory (can be
internal or external)
Device management - ANSWERSinvolves overseeing the delicate balance of the system's finite
supply of devices with the user's almost infinite demand for them
The four basic functions of Device Management - ANSWERS1. Monitoring the status of each
device
2. Enforcing present policies to determine which process gets device and for how long
3. Allocating each device
4. Deallocating each device
bit manipulators - ANSWERSComputers are digital data processors used to turn data into
information.
Computers use at least 3 ways to represent bits - ANSWERSMagnetic, Optical, or Electricity
Magnetic - ANSWERS+ - charge
Optical - ANSWERSabsence or presence of reflective light
Electricity (voltage) - ANSWERSsolid state
,From the OS perspective there are three device types - ANSWERSDedicated, Shared, and Virtual
Dedicated device - ANSWERSAssigned to one job at a time:
- for entire time that job is active (or until released)
- EX. tape drivers, printers, and plotters
Disadvantage:
- must be allocated for duration of job execution - inefficient if device not used 100 percent of
time
Shared device - ANSWERSAssigned to several processes.
- EX. direct access storage device (DASD)
Virtual device - ANSWERSDedicated and shared device combination - dedicated device
transformed into shared device
EX. printer
- converted by spooling program
Spooling - ANSWERSspeeds up slow dedicated I/O device
OS Device Manager divides I/O task into 3 parts - ANSWERSI/O traffic controller, scheduler, and
handler
I/O traffic controller - ANSWERS- Watches status of devices, control units, channels
- Three main tasks:
1. Determine if path available
, 2. If more than one path available, determine which one to select
3. If paths all busy, determine when one is available
- Maintains database containing each unit's status and connections
I/O schedular - ANSWERS- Similar job as process scheduler
- Allocates devices, control units, and channels
- If requests greater than available paths (decides which request to satisfy first: based on
different criteria)
I/O device handler - ANSWERS- Performs actual data transfer
1. Processes device interrupts
2. Handles error conditions
3. Provides detailed scheduling algorithms
- Device dependent
Storage devices are classified by several factors - ANSWERSType of medium: magnetic, optical,
solid state
Access Method: sequential, direct
Capacity: how much can be stored (# bytes)
Access Time: how fast can save \ retrieve data
etc (fixed \ removable).
Sequential Access Storage Media - ANSWERSMagnetic tape
